Sexual activity during late pregnancy and risk of preterm delivery

Objective: To examine the association between sexual activity during late p regnancy and preterm delivery. Methods: Women at least 16 years old and carrying singleton fetuses were re cruited between 24 and 29 weeks' gestation from prenatal clinics in central North Carolina. They were interviewed by telephone about sexual activity b efore and during pregnancy. One hundred eighty-seven women delivered betwee n 29 and 36 weeks and had a follow-up interview after delivery. Four hundre d nine women who were selected randomly from the cohort served as controls and had a follow-up interview between 29 and 36 weeks (mean gestational age 39.2 weeks). Results: Intercourse during late pregnancy was associated with a reduced ri sk of preterm delivery. The conditional odds ratio (OR) was 0.34 and 95% co nfidence interval (CI) 0.23, 0.51 for preterm delivery within 2 weeks after intercourse. Similar decreased risk for preterm delivery was found with re cent female orgasm. Adjusting for race, age, education, and living with a p artner had little effect on results. Cases were more likely than controls t o report poorer health, medical reasons for reducing sexual activity, less interest in sex, and receipt of advice to restrict sexual activity during p regnancy. Results did not differ substantially according to presence or abs ence of bacterial vaginosis at 28 weeks. Conclusion: These data provide evidence against the hypothesis that sexual activity generally increases risk of preterm delivery between 29 and 36 wee ks. However, we cannot exclude the possibility that a small subgroup of sus ceptible women might have adverse consequences of sexual activity. [Obstet Gynecol 2001;97:283-9. (C) 2001 by The American College of Obstetricians an d Gynecologists.).